Marek E. Bialkowski

Design of Ultrawideband Planar Monopole Antennas of Circular and Elliptical Shape

An efficient approach is described for designing ultrawideband (UWB) antennas in the form of planar monopoles of elliptical and circular shape. To avoid the time consuming trial-and-error approach presented in other works, simple design formulas for this type of radiators are described and their validity is tested via electromagnetic analysis and measurements. Full electromagnetic wave investigations are performed assuming three types of substrates with wide range of dielectric constant and thickness. The presented results show that the proposed method can be applied directly to design planar antennas that cover the ultrawide frequency band from 3.1 GHz to more than 10.6 GHz. Four types of monopole antennas were manufactured using RT6010LM substrate and their operation was tested in terms of return loss, radiation pattern characteristics, gain, and time domain response. The developed antennas feature UWB behavior with near omnidirectional characteristics and good radiation efficiency. The time domain transmission tests between two identical elements show that the manufactured circular monopoles offer better performance in terms of distortionless pulse transmission than their elliptically shaped counter parts. These antennas are also assessed in terms of fidelity factor. The manufactured antennas show a high fidelity factor which is more than 90% for the face-to-face orientation.

Improvement of compact terminal antenna performance by incorporating open-end slots in ground plane

This letter describes a new idea of increasing operational bandwidth of a compact planar inverted F antenna (PIFA) by introducing open-end slots in the ground plane under the radiating patch. The slots are not in the way of active modules of a wireless transceiver and thus the proposed antenna size reduction method is attractive from the point of view of practical implementation.

Design of Compact Directional Couplers for UWB Applications

This paper presents a simple design method for a class of compact couplers, which offer coupling in the range of 3-10 dB over an ultra-wide frequency band from 3.1 to 10.6 GHz. The proposed couplers are formed by two elliptically shaped microstrip lines, which are broadside coupled through an elliptically shaped slot. Their design is demonstrated for a 3-, 6-, and 10-dB coupling assuming a 0.508-mm-thick Rogers RO4003C substrate. Results of simulation and measurements show that the designed devices exhibit a coupling of 3plusmn1 dB, 6plusmn1.4 dB and 10plusmn1.5 dB across the 3.1-10.6-GHz band. This ultra-wideband coupling is accompanied by isolation and return loss in the order of 20 dB or better. The manufactured devices including microstrip ports occupy an area of 25 mm times 15 mm

Design of a Compact UWB Out-of-Phase Power Divider

The design of a compact out-of-phase uniplanar power divider operating over an ultra wide frequency band is presented. To achieve an out-of-phase signal division over a large frequency range, a T-junction formed by a slotline and a microstrip line accompanied by wideband microstrip to slotline transitions is employed. The simulated and experimental results of the developed divider show a low insertion loss and good return loss performance of the three ports across the band 3.1-10.6 GHz

Simple Broadband Planar CPW-Fed Quasi-Yagi Antenna

In this letter, we present a novel coplanar waveguide fed quasi-Yagi antenna with broad bandwidth. The uniqueness of this design is due to its simple feed selection and despite this, its achievable bandwidth. The 10 dB return loss bandwidth of the antenna is 44% covering X-band. The antenna is realized on a high dielectric constant substrate and is compatible with microstrip circuitry and active devices. The gain of the antenna is 7.4 dBi, the front-to-back ratio is 15 dB and the nominal efficiency of the radiator is 95%.

Designing a 161-element Ku-band microstrip reflectarray of variable size patches using an equivalent unit cell waveguide approach

We present an equivalent unit cell waveguide approach (WGA) to designing a multilayer microstrip reflectarray of variable size patches. A normal incidence of a plane wave on an infinite periodic array of radiating elements is considered to obtain reflection coefficient phase curves for the reflectarrays elements. It is shown that this problem is equivalent to the problem of reflection of the dominant TEM mode in a waveguide with patches interleaved by layers of dielectric. This waveguide problem is solved using a field matching technique and the method of moments (MoM). Based on this solution, a fast computer algorithm is developed to generate reflection coefficient phase curves for a multilayer microstrip patch reflectarray. The validity of the developed algorithm is tested against alternative approaches and Agilent high frequency structure simulator (HFSS). Having confirmed the validity of the WGA approach, a small offset feed two-layer microstrip patch array is designed and developed. This reflectarray is tested experimentally and shows good performance.

Design of UWB Planar Band-Notched Antenna Using Parasitic Elements

A method is described to reject certain bands within the passband of an ultrawideband (UWB) planar antenna using parasitic elements. In the presented design, the antenna is created by a planar monopole and a ground plane both of half circle shape, whereas parasitic elements are in the form of printed strips. Four examples of UWB antenna design are shown. The first design is without parasitic, while the remaining ones are with parasitics to reject a single narrow band, a wide band or three narrow bands. The results of simulation and measurements show that all these antenna designs exhibit a 10-dB return loss bandwidth from 3 GHz to 11 GHz excluding the rejected bands. More than 10 dB gain drop is recorded in the suppressed bands. The time domain transmission test between two identical antennas without the parasitic strips shows an almost distortionless pulse performance.

Effect of mutual coupling on the interference rejection capabilities of linear and circular arrays in CDMA systems

This paper is concerned with assessing the interference rejection capabilities of linear and circular array of dipoles that can be part of a base station of a code-division multiple-access cellular communication system. The performance criteria for signal-to-interference ratio (SIR) improvement employed in this paper is the spatial interference suppression coefficient. We first derive an expression for this figure of merit and then analyze and compare the SIR performance of the two types of arrays. For a linear array, we quantitatively assess the degradation in SIR performance as we move from array broadside to array end-fire direction. In addition, the effect of mutual coupling is taken into account.

An ultra wideband microwave imaging system for breast cancer detection

An experimental study concerning Ultra Wideband (UWB) Microwave Radar for breast cancer detection is described. A simple phantom, consisting of a cylindrical plastic container with a low dielectric constant material imitating fatty tissues and a high dielectric constant object emulating turnout, is scanned with a tapered slot antenna operating between 3.1 to 10.6 GHz. A successful detection of a target is accomplished by a visual inspection of a two-dimensional image of the scanned phantom.

Circularly polarized aperture-coupled circular microstrip patch antennas for L-band applications

Circularly polarized aperture-coupled circular microstrip patch antennas are investigated with the goal of obtaining an 8% impedance and ellipticity bandwidth in the L-band. Three varieties-a single-feed patch with perturbation segments, a single-feed stacked patch with perturbation segments, and a dual-feed patch with a 3-dB branch line coupler as an external polarizer are considered to obtain the required performance. All the three investigated patch configurations meet the impedance bandwidth requirement, but only two varieties: the single-feed stacked patch and the dual-feed patch meet the required ellipticity bandwidth. These antennas feature more than 9-dBi gain. They use low-cost substrates and foam for bandwidth enhancement and, hence, they are attractive for applications where the production cost is of importance.